Programmable memory devices such as programmable read-only memory (PROM) and one-time programmable read-only memory (OTPROM) are typically programmed by either destroying links (via a fuse) or creating links (via an antifuse) within the memory circuit. In PROMs, for instance, each memory location or bit contains a fuse and/or an antifuse, and is programmed by triggering one of the two. Once programming is performed, it is generally irreversible. The programming is usually done after manufacturing of the memory device, and with a particular end-use or application in mind.
Fuse links are commonly implemented with resistive fuse elements that can be open-circuited or ‘blown’ with an appropriate amount of high-current. Antifuse links, on the other hand, are implemented with a thin barrier layer of non-conducting material (such as silicon dioxide) between two conductor layers or terminals, such that when a sufficiently high voltage is applied across the terminals, the silicon dioxide or other such non-conducting material is effectively turned into a short-circuit or otherwise low resistance conductive path between the two terminals.
Conventional fuse and antifuse links for use in programming memory are associated with a number of problems, including a number of non-trivial design and layout considerations.